The plate-glass cutter lays out rectangular product plates requested to be cut from a rectangular glass blank. In the conventional blank layout method, the direction in which product glass plates being cut are laid out (in the longitudinal or transverse direction), and the direction in which the cutter line is drawn as the cutter travels (in the longitudinal or transverse direction) are determined on the basis of an empirical algorithm. A typical flow chart of the conventional blank layout method is shown in FIG. 1. The data structure referred to as instructions, in which information on a product type being cut (product number, product dimensions, and the number of residual products being cut) is stored, is sorted in the descending order of product area (STEP S1). This is done to improve the total yield by laying out product plates by giving priority to those of larger sizes. Next, the dimensions of a glass blank are set as the initial blank space (STEP S2). Instructions are then extracted sequentially one after another from the instruction list (STEP S3), and the largest possible number of those products are laid out on all the residual blank spaces. There are a plurality of residual blank spaces as the glass blank is divided by cutter lines in laying out products. In order to improve the yield by preferentially laying out products on smaller residual blank spaces, the residual blank spaces are sorted in the ascending order of size (STEP S4), and extracted in that order (STEP S5) to lay out products on the residual blank spaces. When products are laid out on a residual blank space, a product (glass plate) is first laid out in the longitudinal direction, or in the transverse direction if cutting in the longitudinal direction is impossible. The residual products being cut, if any, are laid out continuously in the same direction by extending the cutter line sideways. If only one product is laid out, the cutter line dividing the residual blank spaces is extended in such a direction that larger residual blank spaces are left (STEP S6). The availability of the next residual blank space is judged (STEP S7). If the next residual blank space is not available, divided residual blank spaces are added (STEP S8), the next instruction is extracted (STEP S9), and the same steps are repeated. As described above, the direction in which products are laid out, and the direction in which cutter line is drawn are determined on the basis of an empirical algorithm in the conventional blank layout method. For this reason, only one set of the type of product being laid out, the layout direction and cutter-line direction is sought and used. This prevents the yield from being improved. If one type of product A is laid out on a glass blank 10, as shown in FIG. 2A, for example, only six pieces of products can be laid out in the conventional method. If products A in the lower row are arranged in the transverse direction, as shown in FIG. 2B, however, one more piece of product can be obtained.